accessible category and Ind

Proposition

Let 20241202-accessible_category_and_ind_6504badfb8b176cae5655b0b57f32302a0587b3d.svg be a regular cardinal and 20241202-accessible_category_and_ind_985b96adbc801fbbbe00ac354f4e5f9fa2a8c5dd.svg an infinity category.

TFAE:

  1. 20241202-accessible_category_and_ind_985b96adbc801fbbbe00ac354f4e5f9fa2a8c5dd.svg is a 20241202-accessible_category_and_ind_d09a997b979e82e7400788faa006c0d121254cf8.svg-kappa accessible infinity category.
  2. 20241202-accessible_category_and_ind_1af75d3d8d364b4d6d5ba9553abaae0de41eb31b.svg where 20241202-accessible_category_and_ind_f853b4448d5fd71bc66d30f5620231db30d5b3c8.svg is the full infinity subcategory containing 20241202-accessible_category_and_ind_af44d5b9c78a22caa23e3ac74a202b279cd801c6.svg-compact objects, where 20241202-accessible_category_and_ind_f853b4448d5fd71bc66d30f5620231db30d5b3c8.svg furthermore is essentially small.
  3. there exists a set of 20241202-accessible_category_and_ind_d09a997b979e82e7400788faa006c0d121254cf8.svg-compact objects such that for full subcategory 20241202-accessible_category_and_ind_dc8fc442dddded85f3f5ead0ba0954d560bc5651.svg containing those objects
20241202-accessible_category_and_ind_116af94993c7be773a8e17c14d391a860996cd80.svg
  1. there exists a small infinity category 20241202-accessible_category_and_ind_dc8fc442dddded85f3f5ead0ba0954d560bc5651.svg such that
20241202-accessible_category_and_ind_116af94993c7be773a8e17c14d391a860996cd80.svg

see:

Proof

1) 20241202-accessible_category_and_ind_5667b5be7592236ab833642a1d2a85ce8a5490a6.svg 2)

FW: 6.62
sketch:

The inclusion

20241202-accessible_category_and_ind_19576a307b815df05b4d9898adfaea79f0409e7d.svg

induces a factorization

20241202-accessible_category_and_ind_b24355227d78ce556e21f0117d273dbacade3c37.svg

(cf. universal property of Ind kappa)

one can show, that this induced map is an joyal equivalence (todo :/):

2) 20241202-accessible_category_and_ind_5667b5be7592236ab833642a1d2a85ce8a5490a6.svg 3)

Let 20241202-accessible_category_and_ind_a690c86ae86fd3e846200f0828f0016730db6cbf.svg for some small infinity category 20241202-accessible_category_and_ind_dc8fc442dddded85f3f5ead0ba0954d560bc5651.svg.

Note that each object 20241202-accessible_category_and_ind_76c32a30c15f2c7d9a2e7ddbf31ce94f41a546ac.svg is a retract of some 20241202-accessible_category_and_ind_699c45cde03cc5583ad66a2e4128d5cc21e943d9.svg (where 20241202-accessible_category_and_ind_dc8fc442dddded85f3f5ead0ba0954d560bc5651.svg is identified with the image, cf. compact object as filtered colimit as retract)
This follows from retracts of a small subcategory as essentially small subcategory

3) 20241202-accessible_category_and_ind_5667b5be7592236ab833642a1d2a85ce8a5490a6.svg 4)

special case

Date: nil

Author: Anton Zakrewski

Created: 2024-12-10 Di 11:11